Robin Wood shows a similar broad sweep tool in use in a video on his site. He uses it to undercut the pillar, similar to what seems implied in the German movie, where we see a cut-in to the turner drawing it up from the smoothed bottom. Familiar problem to most, I'm sure, as trying to get a broad area smooth with narrow cuts isn't easy.
I am like Robin in keeping a pillar in my turnings, though for for stability, not power. My normal method leaves a 1/2 button on dead center which is cut or scraped away from center outward so as to avoid the twist and dig that might otherwise occur when coming from the outside inward. His tool seems a good choice for that use.
Just as an aside, I can sure relate to his hollowing problems. Back when I only had broad sweep gouges I used to fingernail grind, though not quite as severely as he, because I also used them for planing and coving in spindle orientations. You have to remove wood slowly with them, because they're not made to plunge.
